A television screen is defined by a large number of image points or pixels. To display a still picture, data needs to be provided to determine the color and intensity of all these pixels. To display a moving picture or movie, such data needs to be provided for a succession of individual still pictures. According to European standards, a video movie contains 25 pictures per second. Thus, displaying a video movie involves a data stream of many megabits per second.
It is noted that, in order to reduce this data stream, it is known to compress the data; depending on the compression technique employed, the inevitable loss of information leads to no or an acceptable degradation of image quality. Nevertheless, it should be clear that a video movie of a certain defined length of time corresponds to a certain amount of data. In transfer, such as broadcast by air or transmission over a network, or from a disc drive to a display, the movie involves a data stream of a certain bit frequency or bandwidth. In storage on a storage medium, such as for instance a hard disc, an optical disc etc., the storage capacity of the storage medium defines a limit to the length of a video stream that can be stored.
There is a tendency towards interactive television, a concept which allows a user to influence the movie he is watching. In one approach, the user is offered a plurality of movies, and the user's influence actually corresponds to a selection of one movie out of the plurality offered. Defined in this way, even the conventional system of a plurality of television channels can be indicated as being “interactive”, since the user has to press a button to make a choice. Actually, this conventional system is illustrative for the conventional way a plurality of movies is made available to a user: the full data of all video streams are provided in parallel. Thus, providing a plurality of N movies takes a bandwidth of N times the bandwidth of one single movie. Likewise, if a storage medium contains N movies stored in a traditional manner, the full data of all video streams being stored, the lengths of the individual movies are reduced by a factor N (assuming all movies have equal length).
Although the present invention is applicable to a situation where a plurality of “different” movies are provided, the present invention relates particularly to a multi-angle or multi-version movie. For instance, a scene is filmed from four different view points or angles, giving in fact four different movies relating to the same scene. When this is offered to a user, the user can choose an angle, and during display he can switch from one angle to another.
As mentioned, in a conventional approach all angles or movie versions are provided in parallel as complete movies. This involves a multiplication of the required bandwidth. Further, a problem is to ensure synchronization between the individual pictures: if a user switches from one angle to another, the local time of the scene must continue undisturbed.
It is an objective of the present invention to overcome or at least reduce the above problems.